As a type of ophthalmic diagnostic devices, tomographic image capturing devices are put into practical use, which utilize optical interference of so-called optical coherence tomography (OCT) to capture tomographic images of ocular fundus. When the horizontal direction, vertical direction, and depth of an ocular fundus are represented by x-direction, y-direction, and z-direction, respectively, such tomographic image capturing devices can acquire tomographic pictures (B-scan pictures) in the xz-direction. In ordinary image capture using the OCT, the tomographic images are captured, for example, at a rate of 40 images per second and a set of 100 or more tomographic pictures of a retina can be acquired by one-time testing (image capture at a part of the retina).
However, such tomographic pictures include a large amount of noise and the like and each raw picture is thus not suitable for tomographic interpretation. In this regard, various methods of image processing have been conventionally proposed to generate high-quality pictures suitable for tomographic interpretation. For example, an adding process is performed on pictures of a set of captured tomographic pictures to generate a picture for tomographic interpretation. Patent Literature 1 discloses a technique of adding and averaging the captured entire two-dimensional tomographic images to generate a tomographic picture with less noise.
To avoid distortion of tomographic pictures due to the effect of involuntary eye movements, high-speed measurement is needed as much as possible. Patent Literature 2 discloses a technique in which, to reduce the time necessary for the measurement, a measurement region is irradiated with a plurality of measurement light beams while being displaced by a small distance and scanned with the beams in the same direction and an adding and averaging process is performed on the obtained plurality of two-dimensional tomographic pictures to generate a tomographic picture with less noise.